Systems and Methods for Detecting Running and Walking Strides and Foot Strikes

ABSTRACT

The present disclosure relates to systems and methods for measuring the location, the amplitude, and/or the direction of forces applied to a walking or running surface. An example system includes a pressure-sensitive sheet that extends along a first axis. The pressure-sensitive sheet includes a top surface and a bottom surface. A vertical force applied at a location along at least one of the top surface or the bottom surface forms an electrical path between the top surface and the bottom surface having a resistance, rf, that is inversely proportional to an amplitude of the vertical force. The system further includes read out circuitry configured to provide information indicative of the amplitude of the vertical force and the location of the vertical force along the first axis of the pressure-sensitive sheet.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims the benefit of U.S. Provisional PatentApplication No. 62/938,742, filed Nov. 21, 2019, the content of which isherewith incorporated by reference.

BACKGROUND

Gait analysis is the study of animal locomotion, more specifically thestudy of human motion, conventionally based on observations of viewers.By studying a person's gait, physical therapists and doctors may be moreable to assess and treat individuals with conditions affecting theirability to walk. Gait analysis is used in sports biomechanics to helpathletes run more efficiently and to identify posture-related ormovement-related problems in people with injuries.

In some conventional applications, gait analysis may be augmented byinstrumentation for measuring body movements, body mechanics, and theactivity of the muscles. For example, an individual may walk or run on atreadmill while being imaged by one or more cameras to measure stridelength and/or other gait characteristics.

However, there exists a need for more effective systems and methods tocharacterize gait and other types of athletic movements and motion.

SUMMARY

The present disclosure generally relates to systems and methods formeasure of the forces during various physical movements such as:running, walking, jumping, lateral change of direction, etc., and thetiming and positions of an individual's feet during such movements.

In a first aspect, a vertical force transducer system is provided. Thevertical force transducer system includes a pressure-sensitive sheetthat extends along a first axis. The pressure-sensitive sheet includes atop surface and a bottom surface. A vertical force applied at a locationalong at least one of the top surface or the bottom surface forms anelectrical path between the top surface and the bottom surface having aresistance, r_(f), that is inversely proportional to an amplitude of thevertical force. The vertical force transducer system also includes readout circuitry configured to provide information indicative of theamplitude of the vertical force and the location of the vertical forcealong the first axis of the pressure-sensitive sheet. The read outcircuitry includes a top electrode extending along the top surface ofthe pressure-sensitive sheet, a bottom electrode extending along thebottom surface of the pressure-sensitive sheet, and a voltage sourceconfigured to provide a reference voltage, V₀, with respect to at leastone of the top electrode or the bottom electrode.

In a second aspect, a lateral force transducer system is provided. Thelateral force transducer system includes a base plate, a top plateslidably coupled to the base plate, and a plurality of friction-reducingelements disposed between the base plate and the top plate. The lateralforce transducer system also includes at least two restraining bracketsdisposed proximate to opposite sides of the base plate. The restrainingbrackets are configured to restrict lateral movement of the top platewith respect to the base plate. The lateral force transducer systemadditionally includes a force sensor coupled to each restrainingbracket. Each force sensor is configured to measure a lateral forceapplied to the top plate and transferred to a given restraining bracket.The lateral force transducer system yet further includes read outcircuitry configured to provide information indicative of an amplitudeof the lateral force and a direction of the lateral force.

In a third aspect, a vertical and lateral force transducer system isprovided. The vertical and lateral force transducer system includes abase plate and a top plate slidably coupled to the base plate. The topplate includes a pressure-sensitive sheet that extends along a firstaxis. The pressure-sensitive sheet includes a top surface and a bottomsurface. A vertical force applied at a location along at least one ofthe top surface or the bottom surface forms an electrical path betweenthe top surface and the bottom surface having a resistance, r_(f), thatis inversely proportional to an amplitude of the vertical force. Thevertical and lateral force transducer system also includes a pluralityof friction-reducing elements disposed between the base plate and thetop plate. The vertical and lateral force transducer system yet furtherincludes at least two restraining brackets disposed proximate toopposite sides of the base plate. The restraining brackets areconfigured to restrict lateral movement of the top plate with respect tothe base plate. The vertical and lateral force transducer system yetfurther includes a force sensor coupled to each restraining bracket.Each force sensor is configured to measure a lateral force applied to agiven restraining bracket. The vertical and lateral force transducersystem additionally includes read out circuitry. The read out circuitryincludes a top electrode extending along the top surface of thepressure-sensitive sheet and a bottom electrode extending along thebottom surface of the pressure-sensitive sheet. The read out circuitryfurther includes a voltage source configured to provide a referencevoltage, V₀, between the top electrode and the bottom electrode. Theread out circuitry is configured to provide information indicative of:the amplitude of the vertical force, the location of the vertical force,the amplitude of the lateral force, and a direction of the lateralforce.

In a fourth aspect, a method is provided. The method includes receiving,from read out circuitry of a vertical force transducer system,information indicative of a vertical force applied to apressure-sensitive sheet. The method also includes determining, based onthe received information, an amplitude of the vertical force anddetermining, based on the received information, a location of thevertical force along a first axis of the pressure-sensitive sheet.

In a fifth aspect, a method is provided. The method includes receiving,from read out circuitry of a lateral force transducer system,information indicative of a lateral force applied to a top plate. Themethod yet further includes determining, based on the receivedinformation, an amplitude of the lateral force and determining, based onthe received information, a direction of the lateral force.

In a sixth aspect, a method is provided. The method includes receiving,from read out circuitry of a vertical and lateral force transducersystem, information indicative of a vertical force and a lateral forceapplied to a top plate. The method additionally includes determining,based on the received information, an amplitude of the vertical force.The method yet further includes determining, based on the receivedinformation, a location of the vertical force along a first axis of apressure-sensitive sheet. The method also includes determining, based onthe received information, an amplitude of the lateral force, anddetermining, based on the received information, a direction of thelateral force.

Other aspects, embodiments, and implementations will become apparent tothose of ordinary skill in the art by reading the following detaileddescription, with reference where appropriate to the accompanyingdrawings.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1A illustrates a vertical force transducer system, according to anexample embodiment.

FIG. 1B illustrates a scenario involving a vertical force transducersystem, according to an example embodiment.

FIG. 2A illustrates a vertical force transducer system, according to anexample embodiment.

FIG. 2B illustrates a vertical force transducer system, according to anexample embodiment.

FIG. 3 illustrates a vertical force transducer system, according to anexample embodiment.

FIG. 4 illustrates equivalent circuits from the vertical forcetransducer system of FIG. 3, according to an example embodiment.

FIG. 5 illustrates mathematical expressions relating to the verticalforce transducer system of FIG. 3, according to an example embodiment.

FIG. 6 illustrates force versus time measurement data, according toexample embodiments.

FIG. 7 illustrates force versus time measurement data, according toexample embodiments.

FIG. 8 illustrates a lateral force transducer system, according to anexample embodiment.

FIG. 9 illustrates a two-dimensional lateral force transducer system,according to an example embodiment.

FIG. 10 illustrates a one-dimensional lateral force transducer system,according to an example embodiment.

FIG. 11 illustrates a vertical and lateral force transducer system,according to an example embodiment.

FIG. 12 illustrates a method, according to an example embodiment.

FIG. 13 illustrates a method, according to an example embodiment.

FIG. 14 illustrates a method, according to an example embodiment.

FIG. 15 illustrates a lateral force transducer system, according to anexample embodiment.

DETAILED DESCRIPTION

Example methods, devices, and systems are described herein. It should beunderstood that the words “example” and “exemplary” are used herein tomean “serving as an example, instance, or illustration.” Any embodimentor feature described herein as being an “example” or “exemplary” is notnecessarily to be construed as preferred or advantageous over otherembodiments or features. Other embodiments can be utilized, and otherchanges can be made, without departing from the scope of the subjectmatter presented herein.

Thus, the example embodiments described herein are not meant to belimiting. Aspects of the present disclosure, as generally describedherein, and illustrated in the figures, can be arranged, substituted,combined, separated, and designed in a wide variety of differentconfigurations, all of which are contemplated herein.

Further, unless context suggests otherwise, the features illustrated ineach of the figures may be used in combination with one another. Thus,the figures should be generally viewed as component aspects of one ormore overall embodiments, with the understanding that not allillustrated features are necessary for each embodiment.

I. Overview

Examples described herein include systems and methods for measure theforces during various physical movements such as: running, walking,jumping, lateral change of direction, etc., and the timing and positionsof an individual's feet during such movements. Measurements of theseforces and the locations of where such forces are applied can be used tocharacterize athletic performance, track recovery from injury, and helpdetermine appropriate footwear, among many other applications. Themeasurements described herein can be analyzed (e.g., with a computingdevice) to provide important diagnostic information to athletes,athletic trainers, doctors, and patients.

An example system may include a plurality of force sensors, which mayutilize force-sensing resistors. In such scenarios, the resistance ofthe force-sensing resistors varies with applied transverse (normal)force. Such force sensors can be disposed both in discrete and extendedgeometries to provide force and distance measurements. Other embodimentsmay additionally or alternatively include other types of force-sensingdevices such as piezo electric devices and/or load cells.

When walking, running, or jumping, forces are applied through the feetof the person moving to the ground surface in both the vertical andhorizontal (e.g., lateral) directions. Vertical force measurements canprovide information on how the foot impacts the ground and theefficiency of this force transfer. Vertical forces can be transferredfrom the ground through the leg of a runner and can cause impactinjuries if the ground/foot vertical contact is excessive. Thehorizontal or lateral forces can provide a measure of strength andacceleration, and the speed and timing of a change in direction.

The systems and methods described herein to characterize foot impactpositions and timing can beneficially provide independent measures ofvelocity and acceleration and can be used to determine how theseparameters vary with distance. This information can be utilized to moreeffectively measure field and track performance, as well as performancein other sports, such as football, soccer, basketball, hockey, andbaseball.

II. Example Devices and Systems

A. Vertical Force Transducer System

FIG. 1A illustrates a vertical force transducer system 100, according toan example embodiment. The vertical force transducer system 100 includesa pressure-sensitive sheet 110 that extends along a first axis (e.g.,along or parallel to a walking and/or running surface or another type ofsurface). The pressure-sensitive sheet 110 includes a top surface 112and a bottom surface 114. An applied force (e.g., a vertical force 10 orforce normal to the pressure-sensitive sheet 110) applied at a locationalong at least one of the top surface 112 or the bottom surface 114forms an electrical path 116 between the top surface 112 and the bottomsurface 114 having a resistance 118, r_(f), that is inverselyproportional to an amplitude of the vertical force 10.

The vertical force transducer system 100 additionally includes read outcircuitry 140. The read out circuitry 140 is configured to provideinformation indicative of the amplitude of the vertical force 10 and thelocation of the vertical force 10 along the first axis of thepressure-sensitive sheet 110.

The read out circuitry 140 includes a top electrode 120 that extendsalong the top surface 112 of the pressure-sensitive sheet 110. The readout circuitry 140 additionally includes a bottom electrode 130 thatextends along the bottom surface 114 of the pressure-sensitive sheet110. The read out circuitry 140 also includes a voltage source 160configured to provide a reference voltage, V₀, between 1) one of: thetop electrode 120 or the bottom electrode 130; and 2) a groundreference.

In some embodiments, the pressure-sensitive sheet 110 could have arectangular shape with a length:width ratio of at least 5:1. Otherlength:width ratios are possible (e.g., 1:1, 2:1, 10:1, 200:1, etc.) andcontemplated within the scope of the present disclosure. In someembodiments, the pressure-sensitive sheet 110 could be a continuoussheet of pressure sensitive material. In other embodiments, thepressure-sensitive sheet 110 could include a plurality of segments ofpressure-sensitive material. In yet another embodiment, thepressure-sensitive sheet 110 and/or other elements of the vertical forcetransducer system 100 could be overlaid and/or integrated into a walking(e.g., a walking path) or running surface (e.g., a running lane orrunning track).

In some embodiments, at least one of the top electrode 120 or the bottomelectrode 114 could have a total resistance, r₀, that is equallydistributed along the first axis of the pressure-sensitive sheet 110. Inother words, the top electrode 120 or the bottom electrode 114 could beselected so as to have a finite resistance (e.g., 10 ohms, 100 ohms, or1000 ohms, or the like). In such scenarios, a resistance measurementalong the length of the top electrode 120 or the bottom electrode 114may provide a two-point resistance value that increases approximatelylinearly with a distance between the two probe points placed along therespective electrode. For example, if the top electrode 112 has a totalresistance, r₀ equal to ten ohms, a two-point probe measurement of abouthalf of the length of the top electrode 120 may indicate approximatelyfive ohms.

In various embodiments, the top electrode 120 or the bottom electrode130 could be a high conductivity electrode. For example, the topelectrode 120 or the bottom electrode 130 could have a resistance ofapproximately zero ohms (e.g., 0.01 ohms, 0.1 ohms, 1 ohms, or thelike). In some embodiments, the high conductivity electrode could beformed from copper and/or another high conductivity, low resistancematerial.

In example embodiments, it will be understood that a first electrode ofthe set of electrodes including the top electrode 120 and the bottomelectrode 130 could have a finite total resistance r₀, while a secondelectrode (e.g., the opposite electrode) could be a high conductivityelectrode. In other words, while the first electrode may have a finiteresistance, the second electrode may be configured to have effectivelyzero resistance.

In some examples, the vertical force transducer system 100 also includesa controller 150. In some embodiments, the controller 150 could includeat least one of a field-programmable gate array (FPGA) or anapplication-specific integrated circuit (ASIC). Additionally oralternatively, the controller 150 may include one or more processors 152and a memory 154. The one or more processors 152 may include ageneral-purpose processor or a special-purpose processor (e.g., digitalsignal processors, etc.). The one or more processors 152 may beconfigured to execute computer-readable program instructions that arestored in the memory 154. As such, the one or more processors 152 mayexecute the program instructions to provide at least some of thefunctionality and operations described herein.

The memory 154 may include or take the form of one or morecomputer-readable storage media that may be read or accessed by the oneor more processors 152. The one or more computer-readable storage mediacan include volatile and/or non-volatile storage components, such asoptical, magnetic, organic or other memory or disc storage, which may beintegrated in whole or in part with at least one of the one or moreprocessors 152. In some embodiments, the memory 154 may be implementedusing a single physical device (e.g., one optical, magnetic, organic orother memory or disc storage unit), while in other embodiments, thememory 154 can be implemented using two or more physical devices.

As noted, the memory 154 may include computer-readable programinstructions that relate to operations of vertical force transducersystem 100. As such, the memory 154 may include program instructions toperform or facilitate some or all of the functionality described herein.The controller 150 is configured to carry out operations. In someembodiments, controller 150 may carry out the operations by way of theprocessor 152 executing instructions stored in the memory 154.

In some embodiments, the operations could include operating variouselements of vertical force transducer system 100 to obtain informationabout the amplitude and/or the location of the vertical force 10. Thecontroller 150 could be configured to carry out other operations aswell.

In example embodiments, the operations could include causing the voltagesource 160 to provide the reference voltage, V₀, between 1) one of: thetop electrode 120 or the bottom electrode 130; and 2) a groundreference.

The operations include receiving, from the read out circuitry 140,information indicative of the vertical force 10 applied to thepressure-sensitive sheet 110. The information could include, forexample, one or more analog or digital signals based on the verticalforce 10.

In various embodiments, the voltages used to calculate the verticalforce 10 (inversely proportional to R_(f)) and the location of theapplied force (x/d), can be measured using a fast analog to digitalconverter (ADC) 156 and a digital computer. An example of a suitable A/Ddevice is a Measurement Computing A/D model USB-202. Such devices arecapable of performing approximately 100,000 A/D conversions per second,which may beneficially provide sufficient time resolution to accuratelyrecord the vertical forces applied to the pressure-sensitive sheet. Asan example, an applied vertical force of a walking or running step mayhave a rise time of a few milliseconds. A suitable ADC may be capable ofdigitizing several different voltages (e.g., 8 different voltages),which can be used to monitor the voltage at each end (e.g. proximate anddistal ends) of both the left and right foot force sensors. A suitablecomputer is manufactured by Dell Corporation Model XPS 15 with a highspeed USB 2.0 interface, which could be configured to accept the highspeed data from the ADC.

The operations include determining, based on the received information,an amplitude of the vertical force 10. In some embodiments, determiningthe amplitude of the vertical force 10 could include calculating anestimated normal force (e.g., 1 Newtons (N), 10 N, 100 N) that is beingapplied to the pressure-sensitive sheet. As described herein,calculating the estimated normal force could be performed by monitoringvoltages at a plurality of voltage nodes in the vertical forcetransducer system.

The operations additionally include determining, based on the receivedinformation, a location, x, of the vertical force 10 along the firstaxis of the pressure-sensitive sheet 110. In some embodiments,determining the location, x, of the vertical force 10 along the firstaxis of the pressure-sensitive sheet 110 could include calculating thelocation, x, based on voltage values measured at each end of the topelectrode 120.

FIG. 1B illustrates a scenario 180 involving the vertical forcetransducer system 100, according to an example embodiment. Scenario 180includes an individual 182 who may walk or run along the vertical forcetransducer system 100. In such an example, the individual 182 may walkor run along the vertical force transducer system 100 so that theindividual's left foot contacts the left foot electrode 120 b and theindividual's right foot contacts the right foot electrode 120 a in analternate, successive fashion. In some examples, the individual 182 mayjump, skip, hop, dance or make other movements along the vertical forcetransducer system 100.

In an example embodiment, a plurality of light-emitter devices 170 a and170 b could be disposed along the sides of the right foot electrode 120a and left foot electrode 120 b, respectively. In some examples, thelight-emitter devices 170 a and 170 b could include light-emittingdiodes (LEDs), organic LEDs (OLEDs), or the equivalent. In suchscenarios, the plurality of light-emitter devices could includeperiodically-spaced LEDs (e.g., one LED per inch). Additionally oralternatively, light-emitter devices 170 a and 170 b could include aone-dimensional or two-dimensional array of LEDs, among otherpossibilities.

In some embodiments, the light-emitter devices could be configured toilluminate in response to at least one of: sensing at least one footfallor a predetermined illumination pattern. For example, light-emitterdevices 170 a and 170 b could be configured to illuminate at locationsproximate to foot strikes (e.g., foot strike location 184). Additionallyor alternatively, light-emitter devices 170 a and 170 b could beconfigured to illuminate based on a predetermined illumination pattern.Such predetermined illumination patterns could include, for example, a“chase” sequence where the individual 182 is challenged to walk or runto keep up with successively-illuminated footfall/stride locations alongthe length of the vertical force transducer system 100. In someexamples, the various locations could be illuminated so that theindividual 182 could “race themselves” and/or “race a celebrity” (e.g.,a world-champion sprinter or long-distance runner, etc.). Additionallyor alternatively, a training mode could provide illuminated footfalllocations in an effort to improve athletic performance and/orrunning/walking form (e.g., speed interval training, triple jump, stridelengthening exercises, etc.). In other embodiments, the light-emitterdevices 170 a and/or 170 b could be configured to fast-blink orslow-blink to indicate a running or walking pace and/or whether theindividual 182 should speed up or slow down their walking or runningpace. In yet further embodiments, the light-emitter devices 170 a and170 b could be illuminated with varying colors to indicate variousactions for the individual 182 to take (e.g., green to indicate run,yellow to indicate jog, red to indicate stop, etc.).

Other activities and/or games could be possible within the scope of thepresent disclosure. For example, users may participate in a game of“hopscotch”, which may include a predetermined hop/jump step pattern.Additionally or alternatively, a game of “tag” could include one or moreblinking light-emitter devices that the individual must “touch” within atime goal. Athletic performance metrics, such as a shuttle run, longjump, 40 yard dash, triple jump, and/or other athletic movements couldbe indicated by utilizing the light-emitter devices 170 a and 170 b andcould be measured by way of the vertical force transducer system 100 asdescribed herein. In such scenarios, systems and methods describedherein could provide spatio-temporal force measurements of physicalperformance that are more accurate than conventional measurement methods(e.g., stopwatch, pressure-pad, light-beam sensors, etc.). Furthermore,the present systems and methods could provide a valuable athletictraining tool to improve athletic performance and individual physicalfitness.

FIGS. 2A and 2B illustrate respective vertical force transducer systems200 and 220, according to example embodiments. The vertical forcetransducer system 200 and/or vertical force transducer system 220 couldbe similar or identical to vertical force transducer system 100, asillustrated and described in reference to FIGS. 1A and 1B.

While the top electrode 120 and the bottom electrode 130 are describedin the singular form in various embodiments described herein, it will beunderstood that the top electrode 120 and/or the bottom electrode 130could include a plurality of respective electrodes. As an example, thetop electrode 120 could include a right top electrode 120 a and a lefttop electrode 120 b, as illustrated and described in reference to FIGS.2A and 2B. Additionally or alternatively, the bottom electrode 130 couldinclude a right bottom electrode 130 a and a left bottom electrode 130 bas illustrated and described in reference to FIG. 2B. In yet otherembodiments, the top electrode 120 and/or the bottom electrode 130 couldinclude more respective electrodes, such as a plurality of five, ten,twenty, or more electrodes.

FIG. 3 illustrates a vertical force transducer system 300, according toan example embodiment. Vertical force transducer system 300 could besimilar or identical to vertical force transducer systems 100, 200, and220 as illustrated and described in reference to FIGS. 1A, 1B, 2A, and2B.

The vertical force transducer system 300 could be operable to quantifyvertical forces and foot impact location using a force-sensitiveresistor fabricated as a thin sheet of plastic film. An example of sucha film is 8 mil thick Velostat, manufactured by 3M. Other types ofelectrically conductive films and/or packaging materials made of apolymeric foil (polyolefins) and impregnated with carbon black arepossible and contemplated. These types of films can be purchased inrolls of many hundreds of feet in length and widths of several feet. Theresistance of this film at any point is quite high (e.g., 1,000 ohms,1,000,000 ohms, or higher) until a vertical force is applied at aspecific location. The resistance at this location is then approximatelyinversely proportional to the applied force. A long running or walkingpath can be constructed by laying out a length of the pressure-sensitivefilm sandwiched between top and bottom electrodes extending along thelength of the pressure-sensitive film. The resistance between theelectrodes will be high until a force is applied to the electrode/filmassembly at a specific point. The resistance will then be inverselyproportional to the applied force. Current will flow between theelectrodes primarily at the point where the force is applied. If one ofthe electrodes, for example the top electrode, is designed to have afinite resistance that varies with its length, then the position of theimpact point and the applied force can be determined by measuring thecurrent flow or voltages at both ends of the running path. The otherelectrode, for example the bottom electrode, could be designed to have atotal low resistance. In such scenarios, the voltage applied to thisbottom electrode is constant along its length. It will be understoodthat the function and/or characteristics of the top electrode and thebottom electrode could be swapped as described herein.

This arrangement allows the measurement of vertical forces caused bystepping on the pressure-sensitive film as well as the location of thefoot strike. Vertical force profiles can be used to measure the type offootfall (such as a heel strike versus a toe strike), the impact or risetime of the force versus time, the asymmetry of the force profiles dueto injury, the length and timing of the stride, and other variables. Asdescribed herein, separate top electrodes can be used to measure leftand right foot forces by including a first (left) electrode proximate toleft foot strikes and a second (right) electrode proximate to right footstrikes.

FIG. 4 illustrates respective equivalent circuits 400 from the verticalforce transducer system 300 of FIG. 3, according to an exampleembodiment. The equivalent circuits 400 could represent respective sidesof the vertical force transducer system 300, as illustrated anddescribed in reference to FIG. 3. FIG. 4 illustrates a left sideequivalent circuit 410 and a right side equivalent circuit 420.

FIG. 5 illustrates mathematical expressions relating to the verticalforce transducer system 300 of FIG. 3, according to an exampleembodiment. In some embodiments, the mathematical expressions could beutilized to calculate the location and/or the amplitude of the verticalforce 10. The following expressions can be obtained by way of nodalcircuit analysis:

R _(d-x) =R ₀·(d−x)/d

R _(x) =R ₀ ·x/d

I _(2R) =V ₀/(R _(d-x) +R _(f) +R ₁₀)

I _(1R) =V ₀/(R _(x) +R _(f) +R ₁₀)

R₀ is the total resistance of top electrode along distance d. V₀ is thevoltage applied to bottom electrode, where the bottom electrode is ahigh conductivity electrode. Thus, V₀ is substantially constant over thedistance d.

V _(1R) =I _(1R) ·R ₁₀

V _(2R) =I _(2R) ·R ₁₀

(V _(1R) +V _(2R))/(V _(1R) ·V _(2R))=[(R _(x) +R _(f) +R ₁₀)+(R _(d-x)+R _(f) +R ₁₀)]/(R ₁₀ ·V ₀)=[R ₀+2·(R _(f) +R ₁₀)]/(R ₁₀ ·V ₀)

R _(f)=[(V _(1R) +V _(2R))/(2·V _(1R) ·V _(2R))]·(R ₁₀ ·V ₀)−R ₁₀−(R₀/2)

(V _(1R) −V _(2R))/(V _(1R) ·V _(2R))=[(R _(x) +R _(f) +R ₁₀)−(R _(d-x)+R _(f) +R ₁₀ R)]/(R ₁₀ ·V ₀)=[R ₀(2x−d)/d]/(R ₁₀ ·V ₀)

x/d=[(V _(1R) −V _(2R))/(V _(1R) ·V _(2R))]R ₁₀ ·V ₀/(2·R ₀)+0.5

x/d=R ₁₀ ·V ₀(V _(1R) −V _(2R))/(2·R ₀ ·V _(1R) ·V _(2R))+0.5

FIG. 6 illustrates force versus time measurement data 600 and 610,according to example embodiments. The vertical force transducer systemsdescribed herein can be used to evaluate running and walking strides.FIG. 6 illustrates force data from a person walking with a standard gaitwhere the heel hits the ground first and then the toe. The x coordinateis time in milliseconds and the y coordinate is force. Note that whenthe left heel hits the ground there is a sudden force impact and yetvery little transfer of weight from the right foot to the left foot.Most of the force impact when walking heel-to-toe is absorbed by thebody and does not effectively transfer weight from one leg to the other.In contrast, while walking so that the toe touches the ground first thebody weight is smoothly transferred from one leg to the other and theforce impact is greatly reduced, potentially lessening the possibilityof injury or degenerative joint wear. Note also that the transfer ofweight from one leg to the other happens more quickly with a toe strike.This data can be used by physical therapists to evaluate gait and toanalyze recovery from joint replacement therapy.

FIG. 7 illustrates force versus time measurement data, according toexample embodiments. FIG. 7 contains data of a person running on thevertical force transducer systems described herein. In this case, therunner was primarily toe striking which is evident from the absence ofany heel strike impact signature. Note that in contrast to walking,there are points in time when neither foot is in contact with theground. In certain situations, for example in professional football,this would be a time when the runner would be more vulnerable to an openfield tackle. Trainers could use this data to adjust running styles andpotentially to optimize athletic performance.

While example embodiments described herein relate to detecting forcesbased on varying voltage and/or resistance measurements, it will beunderstood that other ways to measure physical forces are possible andcontemplated. For example, force-sensing could be performed by detectingchanges in thin film capacitance, similar to applications in capacitivetouch-screen technologies. In such scenarios, embodiments could includean insulator that is coated with a conductive material, which could makeup the top surface 112 and/or top electrode 120. As a human bodyinteracts with the top surface 112 and/or top electrode 120, anassociated electrostatic field could be distorted or dynamicallyaltered. In such a manner, a magnitude of physical force, which may beproportional to the distortion of the electrostatic field, could bemeasured and/or detected. Additionally or alternatively, piezoelectricsensing systems and methods are contemplated.

Various initialization and/or calibration methods are considered andpossible within the scope of the present disclosure. For example, theforce and/or position of a foot strike can be calibrated by applying aknown force at regular distance intervals along the length of thevertical force transducer system 100. For example, a runner can stepusing just his toes (e.g., tip toe) on markers placed every 12 inchesdown the length of the vertical force transducer system 100. In such ascenario, the voltage differences and sums could be read out at each ofthese locations, and the corresponding values can then be stored inand/or compared against a look up table to determine the location andforce of each foot strike for that person when they subsequently rundown the length of the vertical force transducer system 100. Footstrikes that occur between the measurement locations can be determinedby linear interpolation or curve fitting between adjacent locations inthe lookup table.

In some embodiments, the vertical force transducer system 100 could beincorporated into a treadmill running/walking surface. For example, thevertical force transducer system 100 could be fashioned into a loop orbelt that could be driven by a conventional treadmill belt drivemechanism. In such scenarios, the treadmill system could provideinformation about user stride length, balance, form, among otherpossibilities.

In yet further embodiments, the vertical force transducer system 100could be utilized to detect and/or diagnose various physical or mentalailments. For example, individual 182 could walk along the verticalforce transducer system 100 and various gait information, such asbalance, step length, stride length, cadence, speed, dynamic bas,progression line, foot angle, hip angle, and/or squat performance couldbe provided. A medical professional or trainer could utilize suchinformation to diagnose various conditions, including, but not limitedto: cerebral palsy, Parkinson's disease, or other neuromusculardisorders. Additionally or alternatively, medical professionals may beable to ascertain recovery from medical intervention (e.g., muscle ortendon repair, knee/hip replacement, etc.) or provide improvedprosthetic fitting. Other applications are possible and contemplated.

As described herein, the integrated LEDs or light strips along thelength of the vertical force transducer system could illuminate at theprecise locations of the user's foot-strike. These locations could bestored in data files and the foot strikes can be replayed after eachexercise or recalled from any past attempt. Such an LED “playback”feature could provide the ability for users to race themselves,teammates, global users, celebrity athletes, or set desired “goal” footlocations that will appear based on speed, time, and/or stride length.

In some examples, the LED lights could enable a wide variety ofagility/footwork based games and drills. For example, side-to-sideshuffle steps can be programmed to illuminate the light-emitter devicesand turn such devices off when users place their feet within theindicated step-zones. Distinct color patterns can be used with variousfootwork drills due to the flexibility and programmability of the LEDstrips. These enhancements can improve reaction time and brainplasticity in previously unattainable ways. LED-based reaction trainingis not necessarily a new concept; but generally, the systems involvedare not meant for actual impacts and can be damaged by being stepped on.The present system provides for users to actively use force in drillsthat may have previously involved only “waving” a hand or foot over anoptical sensor.

In various embodiments, a coach could illuminate red, green, orange,yellow, and blue lights along the top surface at the same time andindicate that an athlete needs to turn off the orange lights and bluelights only (e.g., by stepping on or near the orange and blue LEDs). Insuch scenarios, integrated LED strips could allow the surface of thevertical force transducer system to provide a “smart” agility ladder.Precise footwork drills such as the “Icky Shuffle”, dance moves, andother footwork exercises can be analyzed in a highly analytical manner,measuring the pace and/or counting the exact number of steps during thedrill, in addition to providing detailed foot placement and balancemetrics.

B. Lateral Force Transducer System

Assessing movement dynamics also requires the measurement of lateralforces. These are more difficult to measure since they cannot bemeasured directly by force sensors as described for the vertical forces.To measure the lateral forces requires a mobile platform with lowlateral resistance to transfer the forces to sensors which measureforces stopping the lateral motion of the platform. Rigid platforms canbe constructed which rest upon bearing surfaces which allow frictionlessmotion of the platform. When a person walks or runs on this platform theplatform will slide in a direction opposite to the person motion. If theplatform is held in place by a restraining bracket then the lateralforce will be transferred to this bracket. A force transducer placedbetween the platform and the bracket will then measure the lateral forcedue to the walking or running motion of the platform. Forces in anydirection can be measured by mounting the platform on bearing surfaceand constraining the motion in all four horizontal directions.

FIG. 8 illustrates a lateral force transducer system 800, according toan example embodiment. The lateral force transducer system 800 includesa base plate 830 and a top plate 810 slidably coupled to the base plate830.

In some embodiments, the lateral force transducer system 800 may alsoinclude a plurality of friction-reducing elements 820 disposed betweenthe base plate 830 and the top plate 810. In various embodiments, thefriction-reducing elements 820 could include at least one of: a ballbearing, a roller bearing, a fluid bearing, or skate wheels. In suchscenarios, at least 64 friction-reducing elements 820 could be disposedin a planar array between the base plate 830 and the top plate 810. Itwill be understood that other devices and/or mechanisms to provide asurface that moves laterally without friction are possible andcontemplated.

The lateral force transducer system 800 also includes at least tworestraining brackets 840 disposed proximate to opposite sides of thebase plate 830. In such scenarios, the restraining brackets 840 areconfigured to restrict lateral movement of the top plate 810 withrespect to the base plate 830.

The lateral force transducer system 800 additionally includes a forcesensor 860 coupled to each restraining bracket 840. Each force sensor860 is configured to measure a lateral force 12 applied to the top plate810 and transferred to a given restraining bracket 840.

The lateral force transducer system 800 also includes read out circuitry870 configured to provide information indicative of the amplitude of thelateral force 12 and a direction of the lateral force 12.

In some embodiments, the lateral force transducer system 800 mayadditionally include a controller (e.g., controller 150) having at leastone processor (e.g., processor 152) and a memory (e.g., memory 154). Insome embodiments, the processor can execute program instructions storedin the memory so as to carry out operations.

The operations include receiving, from the read out circuitry 870,information indicative of the lateral force 12 applied to the top plate810.

The operations may additionally include determining, based on thereceived information, an amplitude of the lateral force 12.

The operations may additionally include determining, based on thereceived information, a direction of the lateral force 12.

In some embodiments, the lateral force transducer system 800 may includea base plate 830 with four sides. In such scenarios, the at least tworestraining brackets 840 could include four total restraining brackets.In those cases, the restraining brackets 840 could be disposed proximateto each side of the base plate 830 (e.g., along the North, South, East,West sides of the base plate 830).

In some embodiments, the direction of the lateral force 12 could includea force vector parallel to the base plate 830.

In some embodiments, the top plate 810 could include a plurality ofbearing tracks configured to slidably interact with thefriction-reducing elements 820.

FIG. 9 illustrates a two-dimensional lateral force transducer system900, according to an example embodiment. The two-dimensional lateralforce transducer system 900 is a size-scalable force sensing platformdesigned to measure horizontal forces during kinesthetic movement. Thetwo-dimensional lateral force transducer system 900 could be formed bytwo 4′×4′¾″ plywood boards, sixty four 1″ ball-bearing rollers, eight46″×1″×0.0.125″ steel bars, four 3′ aluminum L brackets, and four forcesensors attached to circuit boards. The 64 roller ball bearingassemblies (e.g., Harbor Freight, 1 in. Roller Ball Bearing) are screweddown in an equidistant 8×8 grid across the bottom plywood board. Theeight steel bars are screwed into the underside of the top plywoodboard, in parallel, aligned directly on top of the same 8×8 grid as theball bearing rollers. The top plywood board lays directly on top of thebottom plywood board with the steel tracks on the underside of the topboard providing a frictionless surface for the ball bearings to move andprevents potential indentations in the plywood. All four aluminum Lbrackets are also screwed down to the bottom plywood boards along thefour edges and extended very slightly off the platform. Force sensorsare attached to the center of the aluminum L brackets along all foursides of the bottom board.

Alternatives to using ball-bearing rollers or other bearing assembliesto provide a low friction interface between the top and bottom boardsare: (1) A polymer gel with low lateral or shear force viscosity such asSHOCKtec® Gel, from Shocktec, Inc.; (2) an air bearing surface; (3) acaptured liquid interface (e.g., similar to a waterbed) placed betweenthe top and bottom surface. All these alternatives have low lateralresistance to small displacements of the top surface platform and allowthe lateral force to be applied directly to the force sensor, similar tothe bearing assembly design mentioned above.

As a user moves while on the platform, the extra space provided by the Lbrackets allows very slight movements of the top board which pushes theboard into the force sensor pressure plates in the correspondingdirection of the forces applied. The roller ball assemblies allowmovement—and detection of forces—in all 4 directions simultaneously. Theamount of movement is virtually undetectable by the user to preventcompensatory movements to stabilize the board and can provide anexperience as similar as possible to kinesthetic movement across flatground. These forces are recorded as “North, South, East, or West”horizontal forces and the total horizontal force can be calculated bycombining the force vectors recorded by each direction during thecontact with the board.

FIG. 10 illustrates a one-dimensional lateral force transducer system1000, according to an example embodiment. Lateral force platforms can beconstructed using or cylindrical bearing assemblies (Skate Wheel,Ultimation, 5 foot, conveyor rails, 10779). Skate wheel assemblies 1040allow force measurements both along the direction of motion and in theopposite direction. They also provide a greater contact area between thebearing surface and the top platform 1030 reducing the possibility ofwear. By taking readings from multiple sensors, force vectors in anydirection can be measured.

In some embodiments, the side restraining brackets 1010 a and 1010 bparallel to the lateral force flow in FIG. 10 could include a lowfriction covering or coating, such as polytetrafluoroethylene (PTFE), toreduce frictional forces that might impede the lateral motion of the topplatform 1030. Additionally or alternatively, the side restrainingbrackets 1010 a and 1010 b could incorporate wheel bearing assemblies1040 to constrain the side-to-side motion of the top platform 1030 butstill allow low friction movement in the lateral direction.

In some embodiments, the force sensor restraining brackets 1020 a and1020 b illustrated in FIG. 10 could incorporate a compressible elastomersheet or mechanical spring assemblies. The clamping force applied to therestraining brackets 1020 a and 1020 b during assembly of the lateralforce platform can provide an adjustable preloading of the forcesensors; that is, they will register a force with no additional lateralforce applied to the top platform. This embodiment of the lateral forceplatform will allow each force sensor to measure additional forcesapplied to the top platform in either the forward or reverse directions.

C. Vertical and Lateral Force Transducer System

Systems that can measure both lateral and vertical forces are nowdescribed.

FIG. 11 illustrates a vertical and lateral force transducer system 1100,according to an example embodiment. The vertical and lateral forcetransducer system 1100 could include elements of the vertical forcetransducer system 100, 200, 220, or 300 as illustrated and described inreference to FIGS. 1A, 1B, 2A, 2B, and 3. Additionally, the vertical andlateral force transducer system 1100 could include elements of thelateral force transducer system 800, 900, and/or 1000, as illustratedand described in FIGS. 8, 9, and 10.

The vertical and lateral force transducer system 1100 includes a baseplate (e.g., base plate 830) and a top plate (e.g., top plate 810)slidably coupled to the base plate. The top plate includes apressure-sensitive sheet (e.g., pressure-sensitive sheet 110) thatextends along a first axis. The pressure-sensitive sheet includes a topsurface and a bottom surface. In such scenarios, a vertical force (e.g.,vertical force 10) applied at a location along at least one of the topsurface (e.g., top surface 112) or the bottom surface (e.g., bottomsurface 114) forms an electrical path between the top surface and thebottom surface having a resistance, r_(f), that is inverselyproportional to an amplitude of the vertical force 10.

The vertical and lateral force transducer system 1100 may additionallyinclude a plurality of friction-reducing devices (e.g.,friction-reducing elements 820) disposed between the base plate and thetop plate.

The vertical and lateral force transducer system 1100 may furtherinclude at least two restraining brackets (e.g., restraining brackets840) disposed proximate to opposite sides of the base plate. In such ascenario, the restraining brackets are configured to restrict lateralmovement of the top plate with respect to the base plate.

The vertical and lateral force transducer system 1100 further includes aforce sensor (e.g., force sensor 860) coupled to each restrainingbracket. Each force sensor is configured to measure a lateral force(e.g., lateral force 12) applied to a given restraining bracket.

The vertical and lateral force transducer system 1100 also include readout circuitry (e.g., read out circuitry 1140). The read out circuitrycould include a top electrode (e.g., top electrode 120 extending alongthe top surface of the pressure-sensitive sheet.

The vertical and lateral force transducer system 1100 further includes abottom electrode (e.g., bottom electrode 130) extending along the bottomsurface of the pressure-sensitive sheet.

In some embodiments, the vertical and lateral force transducer system1100 could include a voltage source (e.g., voltage source 160)configured to provide a reference voltage, V₀, between the top electrodeand the bottom electrode. wherein the read out circuitry is configuredto provide information indicative of: the amplitude of the verticalforce, the location of the vertical force, the amplitude of the lateralforce, and a direction of the lateral force.

The vertical and lateral force transducer system 1100 may include acontroller having at least one processor and a memory.

The processor executes program instructions stored in the memory so asto carry out operations. The operations include receiving, from the readout circuitry, information indicative of the vertical and lateral forcesapplied to the top plate. The operations also include determining, basedon the received information, an amplitude of the vertical force.

In some embodiments, the operations could include determining, based onthe received information, a location of the vertical force along thefirst axis of the pressure-sensitive sheet.

The operations may additionally include determining, based on thereceived information, an amplitude of the lateral force.

The operations may further include determining, based on the receivedinformation, a direction of the lateral force.

In some embodiments, the base plate includes four sides. In suchscenarios, at least two restraining brackets may actually describe fourrestraining brackets (one for each side the base plate. In suchscenarios, the restraining brackets could be disposed proximate to eachside of the base plate.

In various embodiments, the direction of the lateral force 12 couldinclude a force vector parallel to the base plate.

In some examples, the friction-reducing elements could include at leastone of: a ball bearing, a roller bearing, a fluid bearing, or skatewheels. As just one example, at least 64 friction-reducing elementscould be disposed in a planar array between the base plate and the topplate.

In some embodiments, the top plate includes a plurality of bearingtracks configured to slidably interact with the friction-reducingelements.

In some embodiments, the vertical force transducer system and thelateral force transducer could be configured to measure both horizontaland vertical forces, creating a complete force profile of an individualfoot strike and other athletic movements including change ofdirection(cuts), jumps, and sudden deaccelerations.

D. Applications of the Vertical and Lateral Force Measurements

Systems described herein represent new and better ways to analyzemovement fundamentals and assess the forces generated by all levels ofhuman movement, from elderly patients undergoing physical therapy toathletes seeking the apexes of human ability. Force profiles can helpphysical therapists by taking baseline measurements pre/post surgery, oras part of their initial body assessment. These baselines can dictateboth the amount of rehabilitation needed to reach pre-injury performanceas well as set realistic expectations based on the force readings ofothers in their demographic.

Systems described herein may beneficially provide athletes and theirtraining staff the opportunity to use previously recorded metrics fromcurrent and previous performance in movement tests to optimize theirtraining and scores in competition. Data on force generated throughmovement may give training staff early warning signs regarding injury,fatigue, or suggest specific exercises that an athlete should focus onto improve their performance.

A common metric to measure speed and acceleration for all positions inAmerican Football is the 40 yard dash. For aspiring professionalfootball players, fractions of a second in a 40 yard dash time can be afactor in draft position and may represent a difference of millions ofdollars in professional contracts. Traditionally, the 40 yard dash hasbeen measured by stopwatches and laser activated timing gates. Withsystems described herein, complex metrics of each individual foot strikecan be analyzed by coaches and trainers. Different lengths of a verticalforce transducer system (e.g., system 100), a lateral force transducersystem (e.g., system 800), and/or a vertical and lateral forcetransducer system (e.g., system 1100) can be used depending on theresources and training space available to the user. As an example, thepath length could range from a 5′-long starting block segment thatmeasures the acceleration and foot-falls of the first few footstrikesplus the horizontal forces of their take off, to a complete 40yard-length segment that tracks data on every footfall of the entireexercise.

In professional athletics, there is a great need for both therehabilitation of lower-body injuries as well as proper training toreach peak performance. The rigors of high-level athletic competitionpropel the human body to the limits of our physical capabilities whilealso resulting in higher rates of devastating injury. As footballplayers have gotten stronger, faster, and more explosive, the risk ofcareer-altering injuries such as ACL tears has also increased. One suchinjury to a star athlete can dramatically change the outcome of theircareer, as well as possibly affect the success of the injured athlete'steam.

Anterior cruciate ligament (ACL) tears are one of the most commoncatastrophic injuries suffered by athletes of all ages. These injuriesare most likely to occur during sports involving sudden changes ofdirection, such as basketball, football, and soccer. Recovery time foran ACL reconstruction typically takes no less than 9 months and someresearch indicates a more realistic timeline may be more than two years.In some cases, the athlete never returns to pre-injury levels ofactivity or function. Due to the severity of this injury and the lengthyand laborious rehabilitation process, there has been recent emphasis indeveloping realistic and evidence-based “Return to Sport” guidelines forathletes trying to return to athletic competition.

Return to Sport guidelines involve helping athletes reach pre-injurybaseline levels of function, primarily post reconstructive ACL surgery,before returning to intensive activity. One of the most common Return ToSport tests is the “single leg hop test”. In this test, the athletejumps forward with one leg as far as possible and lands with the sameleg. The distance is recorded for each jump and the process is repeatedtwice, with both the injured and noninjured leg. Despite this being anindustry standard test, there is some conflicting research on theefficacy of the “single leg hop test” for ACL reconstruction recovery.Research has shown that the degradation of function in the non-injuredleg during the 6-12+ month rehabilitation process may impact theefficacy of this test as a Return To Sport standard.

Embodiments described herein can help inform new Return To Sportguidelines by giving athletic teams, athletic trainers, physicaltherapists, and other fitness professionals access to data that compilesthe complete force profile (e.g., combination of both vertical andlateral force) of a given athlete. Coaches and Physical Therapists willgain access to previously unattainable data from these platforms anddevelop complete force profiles of virtually any form of body movementexercise. The complete force profiles measured by these systems will bea novel resource to validate and enhance current testing criteria andpotentially influence new Return To Sport guidelines across the entiresports world.

III. Example Methods

FIG. 12 illustrates a method 1200, according to an example embodiment.It will be understood that the method 1200 may include fewer or moresteps or blocks than those expressly illustrated or otherwise disclosedherein. Furthermore, respective steps or blocks of method 1200 may beperformed in any order and each step or block may be performed one ormore times. In some embodiments, some or all of the blocks or steps ofmethod 1200 may be carried out by a vertical force transducer system(e.g., vertical force transducer system 100). It will be understood thatother scenarios are possible and contemplated within the context of thepresent disclosure.

Block 1202 includes receiving, from read out circuitry of a verticalforce transducer system, information indicative of a vertical forceapplied to a pressure-sensitive sheet.

Block 1204 includes determining, based on the received information, anamplitude of the vertical force.

Block 1206 includes determining, based on the received information, alocation of the vertical force along a first axis of thepressure-sensitive sheet.

FIG. 13 illustrates a method 1300, according to an example embodiment.It will be understood that the method 1300 may include fewer or moresteps or blocks than those expressly illustrated or otherwise disclosedherein. Furthermore, respective steps or blocks of method 1300 may beperformed in any order and each step or block may be performed one ormore times. In some embodiments, some or all of the blocks or steps ofmethod 1300 may be carried out by a lateral force transducer system(e.g., lateral force transducer system 800). It will be understood thatother scenarios are possible and contemplated within the context of thepresent disclosure.

Block 1302 includes receiving, from the read out circuitry of a lateralforce transducer system, information indicative of a lateral forceapplied to a top plate.

Block 1304 includes determining, based on the received information, anamplitude of the lateral force.

Block 1306 includes determining, based on the received information, adirection of the lateral force.

FIG. 14 illustrates a method 1400, according to an example embodiment.It will be understood that the method 1400 may include fewer or moresteps or blocks than those expressly illustrated or otherwise disclosedherein. Furthermore, respective steps or blocks of method 1400 may beperformed in any order and each step or block may be performed one ormore times. In some embodiments, some or all of the blocks or steps ofmethod 1400 may be carried out by a vertical and lateral forcetransducer system (e.g., vertical and lateral force transducer system1100). It will be understood that other scenarios are possible andcontemplated within the context of the present disclosure.

Block 1402 includes receiving, from read out circuitry of a vertical andlateral force transducer system, information indicative of a verticalforce and a lateral force applied to a top plate;

Block 1404 includes determining, based on the received information, anamplitude of the vertical force.

Block 1406 includes determining, based on the received information, alocation of the vertical force along a first axis of thepressure-sensitive sheet.

Block 1408 includes determining, based on the received information, anamplitude of the lateral force.

Block 1410 includes determining, based on the received information, adirection of the lateral force.

IV. Additional Example Embodiments

When measuring forces generated from running movements, vertical andlateral forces generated by a runner's left and right feet typicallyoccur at different times (e.g., in an alternating right-left-right-leftmanner). For example, after an initial starting phase (e.g., initialtake-off), the runner's feet alternate contact with the ground andtypically do not land on or push off the ground at the same time.

However, in some scenarios, lateral forces may be produced by both feetsimultaneously during the initial starting phase. For example, duringvarious track and field events, starting blocks may be utilized toprovide that all participants start from equal starting positions andalso to prevent the athletes' feet from slipping upon take-off. In suchscenarios, both feet may be placed on independent starting blocks thatcan be anchored to the running surface. As such, the starting blocks canallow simultaneous lateral force impulses from both legs. The startingblocks can be adjusted to different angles and foot-spacing based on thephysical characteristics and preferences of the athlete.

Within the context of the present disclosure, valuable data can becollected by attaching the starting blocks to lateral force transducerplatforms. Such lateral force transducer platforms may be configured tosimultaneously and independently measure the lateral forces of both feetgenerated during an athlete's take-off from the starting blocks. In anexample embodiment, each starting block may be coupled to a separatelateral force platform. In such scenarios, the timing and forcetransients of the left and right foot may be measured independently.Additionally or alternatively, the vertical and/or lateral forcetransducers described herein may be coupled or affixed directly into oronto the starting blocks themselves.

Track and field events are routinely decided by hundredths of seconds,making precise data on power, speed, and reaction time extremelyvaluable to coaches and athletes of all levels. Accordingly,quantitative data from lateral force transducers mounted on startingblocks could give athletes, trainers, and coaches previously unavailablemetrics on an athlete's explosive power and reaction time relative tothe starting gun. Additionally or alternatively, such embodiments mayinform important adjustments to the starting block angle, length betweenblocks, and transference of lateral force impulse from left to rightfoot, to ensure an athlete is producing their optimal force upontakeoff.

FIG. 15 illustrates a lateral force transducer system 1500, according toan example embodiment. Lateral force transducer system 1500 couldinclude elements that may be similar or identical to lateral forcetransducer system 800, two-dimensional lateral force transducer system900, and/or one-dimensional lateral force transducer system 1000, asillustrated and described in relation to FIGS. 8, 9, and 10,respectively.

According to an example embodiment, the lateral force transducer system1500 includes a base plate (e.g., base plate 1540 a and 1540 b). It willbe recognized that while FIG. 15 illustrates two base plates, a singlebase plate (e.g., common base plate) could be utilized in someembodiments. The base plate could be configured to be removably attachedto a running surface (e.g., track surface). In some embodiments, thebase plate could be embedded in or recessed into the running surface soas to provide a flat walking/running surface.

In such scenarios, the lateral force transducer system 1500 includes afirst top plate 1530 a, which may be slidably coupled to the base plate1540 a. Additionally, the lateral force transducer system 1500 includesa second top plate 1530 b that is slidably coupled to the base plate1540 b.

The lateral force transducer system 1500 also includes a first startingblock 1510 and a second starting block 1512. The first starting block1510 could be affixed or otherwise coupled to the first top plate 1530a. The second starting block 1512 could be affixed or otherwise coupledto the second top plate 1530 b.

In some embodiments, lateral force transducer system 1500 could includea plurality of friction-reducing elements 1550 disposed between thefirst base plate 1540 a and the first top plate 1530 a and between thesecond base plate 1540 b and the second top plate 1530 a.

The lateral force transducer system 1500 also includes a firstrestraining bracket 1560 a configured to restrict lateral movement ofthe first top plate 1530 a with respect to the base plate 1540 a.Furthermore, the lateral force transducer system 1500 includes a secondrestraining bracket 1560 b configured to restrict lateral movement ofthe second top plate 1530 b with respect to the base plate 1540 b.

Additionally, the lateral force transducer system 1500 includes a forcesensor 1570 coupled to each restraining bracket 1560. For example, afirst force sensor 1570 a could be coupled to the first restrainingbracket 1560 a and a second force sensor 1570 b could be coupled to thesecond restraining bracket 1560 b. Each force sensor 1570 a and 1570 bis configured to measure a lateral force applied to the respective topplate 1530 a and 1530 b and transferred to a given restraining bracket1560 a and 1560 b.

Yet further, the lateral force transducer system 1500 includes read outcircuitry configured to provide information indicative of an amplitudeof the lateral force and a direction of the lateral force. For example,the read out circuitry could include an ADC (e.g., ADC 156) and/or acontroller (e.g., controller 150). Additionally or alternatively, thelateral force transducer system 1500 could be configured to be operablycoupled and/or communicatively coupled to another computing device.

The particular arrangements shown in the Figures should not be viewed aslimiting. It should be understood that other embodiments may includemore or less of each element shown in a given Figure. Further, some ofthe illustrated elements may be combined or omitted. Yet further, anillustrative embodiment may include elements that are not illustrated inthe Figures.

A step or block that represents a processing of information cancorrespond to circuitry that can be configured to perform the specificlogical functions of a herein-described method or technique.Alternatively or additionally, a step or block that represents aprocessing of information can correspond to a module, a segment, or aportion of program code (including related data). The program code caninclude one or more instructions executable by a processor forimplementing specific logical functions or actions in the method ortechnique. The program code and/or related data can be stored on anytype of computer readable medium such as a storage device including adisk, hard drive, or other storage medium.

The computer readable medium can also include non-transitory computerreadable media such as computer-readable media that store data for shortperiods of time like register memory, processor cache, and random accessmemory (RAM). The computer readable media can also includenon-transitory computer readable media that store program code and/ordata for longer periods of time. Thus, the computer readable media mayinclude secondary or persistent long term storage, like read only memory(ROM), optical or magnetic disks, compact-disc read only memory(CD-ROM), for example. The computer readable media can also be any othervolatile or non-volatile storage systems. A computer readable medium canbe considered a computer readable storage medium, for example, or atangible storage device.

While various examples and embodiments have been disclosed, otherexamples and embodiments will be apparent to those skilled in the art.The various disclosed examples and embodiments are for purposes ofillustration and are not intended to be limiting, with the true scopebeing indicated by the following claims.

What is claimed is:
 1. A vertical force transducer system, comprising: apressure-sensitive sheet that extends along a first axis, wherein thepressure-sensitive sheet comprises a top surface and a bottom surface,wherein a vertical force applied at a location along at least one of thetop surface or the bottom surface forms an electrical path between thetop surface and the bottom surface having a resistance, r_(f), that isinversely proportional to an amplitude of the vertical force; and readout circuitry configured to provide information indicative of theamplitude of the vertical force and the location of the vertical forcealong the first axis of the pressure-sensitive sheet, wherein the readout circuitry comprises: a top electrode extending along the top surfaceof the pressure-sensitive sheet; a bottom electrode extending along thebottom surface of the pressure-sensitive sheet; and a voltage sourceconfigured to provide a reference voltage, V₀, with respect to at leastone of: the top electrode or the bottom electrode.
 2. The vertical forcetransducer system of claim 1, wherein the pressure-sensitive sheetcomprises a characteristic resistance variation along the first axis. 3.The vertical force transducer system of claim 1, wherein at least one ofthe top electrode or the bottom electrode has a total resistance, r₀,that is equally distributed along the first axis of thepressure-sensitive sheet.
 4. The vertical force transducer system ofclaim 1, wherein at least one of the top electrode or the bottomelectrode comprises a plurality of respective electrodes.
 5. Thevertical force transducer system of claim 1, further comprising acontroller having at least one processor and a memory, wherein theprocessor executes program instructions stored in the memory so as tocarry out operations, the operations comprising: causing the voltagesource to provide the reference voltage, V₀, between the top electrodeand the bottom electrode; receiving, from the read out circuitry,information indicative of the vertical force applied to thepressure-sensitive sheet; determining, based on the receivedinformation, an amplitude of the vertical force; and determining, basedon the received information, a location of the vertical force along thefirst axis of the pressure-sensitive sheet.
 6. The vertical forcetransducer system of claim 1, further comprising a plurality oflight-emitter devices disposed along the top surface, wherein thelight-emitter devices are configured to illuminate in response to atleast one of: sensing at least one footfall or a predeterminedillumination pattern.
 7. A lateral force transducer system, comprising:a base plate; a top plate slidably coupled to the base plate; aplurality of friction-reducing elements disposed between the base plateand the top plate; a force sensor coupled to each restraining bracket,wherein each force sensor is configured to measure a lateral forceapplied to the top plate and transferred to a given restraining bracket;and read out circuitry configured to provide information indicative ofan amplitude of the lateral force and a direction of the lateral force.8. The lateral force transducer system of claim 7, further comprising acontroller having at least one processor and a memory, wherein theprocessor executes program instructions stored in the memory so as tocarry out operations, the operations comprising: receiving, from theread out circuitry, information indicative of the lateral force appliedto the top plate; determining, based on the received information, anamplitude of the lateral force; and determining, based on the receivedinformation, a direction of the lateral force.
 9. The lateral forcetransducer system of claim 7, further comprising at least tworestraining brackets disposed proximate to opposite sides of the baseplate, wherein the restraining brackets are configured to restrictlateral movement of the top plate with respect to the base plate,wherein the base plate comprises four sides, wherein the at least tworestraining brackets comprise four restraining brackets, and wherein therestraining brackets are disposed proximate to each side of the baseplate.
 10. The lateral force transducer system of claim 9, wherein thedirection of the lateral force comprises a force vector parallel to thebase plate.
 11. The lateral force transducer system of claim 7, whereinthe friction-reducing elements comprise at least one of: a ball bearing,a roller bearing, a fluid bearing, or skate wheels.
 12. The lateralforce transducer system of claim 11, wherein a plurality offriction-reducing elements are disposed in a planar array between thebase plate and the top plate.
 13. The lateral force transducer system ofclaim 7, wherein the top plate comprises a plurality of bearing tracksconfigured to slidably interact with the friction-reducing elements. 14.A vertical and lateral force transducer system, comprising: a baseplate; a top plate slidably coupled to the base plate, wherein the topplate comprises: a pressure-sensitive sheet that extends along a firstaxis, wherein the pressure-sensitive sheet comprises a top surface and abottom surface, wherein a vertical force applied at a location along atleast one of the top surface or the bottom surface forms an electricalpath between the top surface and the bottom surface having a resistance,r_(f), that is inversely proportional to an amplitude of the verticalforce; a plurality of friction-reducing elements disposed between thebase plate and the top plate; a force sensor coupled to at least onerestraining bracket, wherein each force sensor is configured to measurea lateral force applied to a given restraining bracket; and read outcircuitry comprising: a top electrode extending along the top surface ofthe pressure-sensitive sheet; a bottom electrode extending along thebottom surface of the pressure-sensitive sheet; and a voltage sourceconfigured to provide a reference voltage, V₀, between one of: the topelectrode or the bottom electrode and a ground reference, wherein theread out circuitry is configured to provide information indicative of:the amplitude of the vertical force, the location of the vertical force,the amplitude of the lateral force, and a direction of the lateralforce.
 15. The vertical and lateral force transducer system of claim 14,further comprising a controller having at least one processor and amemory, wherein the processor executes program instructions stored inthe memory so as to carry out operations, the operations comprising:receiving, from the read out circuitry, information indicative of thevertical and lateral forces applied to the top plate; determining, basedon the received information, an amplitude of the vertical force;determining, based on the received information, a location of thevertical force along the first axis of the pressure-sensitive sheetdetermining, based on the received information, an amplitude of thelateral force; and determining, based on the received information, adirection of the lateral force.
 16. The vertical and lateral forcetransducer system of claim 14, further comprising at least tworestraining brackets disposed proximate to opposite sides of the baseplate, wherein the restraining brackets are configured to restrictlateral movement of the top plate with respect to the base plate,wherein the base plate comprises four sides, wherein the at least tworestraining brackets comprise four restraining brackets, and wherein therestraining brackets are disposed proximate to each side of the baseplate.
 17. The vertical and lateral force transducer system of claim 16,wherein the direction of the lateral force comprises a force vectorparallel to the base plate.
 18. The vertical and lateral forcetransducer system of claim 14, wherein the friction-reducing elementscomprise at least one of: a ball bearing, a roller bearing, a fluidbearing, or skate wheels.
 19. The vertical and lateral force transducersystem of claim 18, wherein a plurality of friction-reducing elementsare disposed in a planar array between the base plate and the top plate.20. The vertical and lateral force transducer system of claim 14,wherein the top plate comprises a plurality of bearing tracks configuredto slidably interact with the friction-reducing elements.